A Bird Blog with Kate St. John

Archive for June, 2013

Though Pitt’s peregrines, Dorothy and E2, are courting again today’s solstice will change that.

All living things have endogenous biological clocks that can run without light cues but we get out of synch with each other and the seasons in the absence of our external timekeeper, the sun. Today our clocks struck twelve and began to head down again.

For peregrines in northern mid-latitudes the summer solstice ends their breeding cycle (initiated by the winter solstice) and triggers molting and preparation for migration.

Molting is a chilly and energy intensive activity in which birds replace all their feathers. Since feathers provide warmth it’s cold to lose them. Growing thousands of new feathers requires protein, increased blood to the feather sites, and changes in the birds’ calcium distribution. And while flight feathers are being replaced flying is somewhat less efficient, an important consideration for precision-flying peregrines.

It makes sense to schedule this activity for a time when food is abundant and temperatures are warm. Dorothy and E2 molt their flight feathers in July and August. Good timing!

Our peregrines don’t migrate but arctic peregrines face an additional challenge. They begin their molt in the arctic but don’t have time to complete it before they must leave on migration. Their bodies have adapted by starting the molt in the arctic, pausing during migration, and resuming at their wintering grounds in South America. Very ingenious!

The lyrics of the Beatles’ Blackbird song used to puzzle to me. What blackbird sings in the dead of night? In eastern North America I didn’t know of any blackbirds that did that.

My worldview was too small. North American blackbirds are icterids: Brewer’s, red-winged, rusty, tri-colored and yellow-headed. In England common blackbirds are thrushes, a single species Turdus merula similar to the American robin.

The common blackbird’s song is complex, varied and beautiful. His syrinx allows him to sing two songs simultaneously and even harmonize with himself. In the video above he starts out loudly on a perch, then drops to the ground and whisper-sings just like a robin. Like our robins he also sings at night.

When I saw this cute photo by Meredith Lombard I knew I had to write about baby porcupines but I soon learned that the truth about these rodents is stranger than fiction.

For starters, baby porcupines are called porcupettes.

Each porcupette is a precocial only child, born with open eyes, well formed teeth, a full coat of fur, and able to climb trees a few hours after birth. In only two weeks he eats green plants. In three months, he’s weaned.

Like his parents he has three kinds of fur: a woolly undercoat, long coarse guard hairs, and sharp hollow quills with barbs at the tip that slant backward. When born his quills are soft and harmless (good thing for his mother!) but within half an hour they’ve stiffened into the protective coat that saves his life. The only place he doesn’t have quills is on his belly — just like his parents.

Neither he nor his parents “throw” their quills but the quills are so loosely attached that they stick easily to any critter that comes close. That includes dad when he approaches mom to conceive a porcupette. Needless to say copulation is a very careful business. No hugs are involved, but there’s a lot of courting to get her in the mood. Dad whines and dances on three legs, showing her his equipment. When she says “You’re the one” he showers her with urine. Then they mate.

I’m not kidding.

All of this happens in October or November. Seven months later: a porcupette.

In all my previous experience, Dorothy and E2 have always had other young to feed and teach after the death of a juvenile. Dorothy would mourn for a day while E2 took care of the “kids.” Then Dorothy would pick up where she left off and family life would return to normal.

But this year with only one fledgling their parenting duties ended abruptly last Friday. Instead of mourning they are courting.

When peregrines lose their entire clutch of eggs they immediately resume courtship and lay a second clutch within 14 days. The earlier in the season this happens, the more likely the second clutch will succeed and fledge. A complete and early loss of fledglings might trigger the courtship reaction.

On the afternoon of Silver Boy’s death E2 invited Dorothy to bow with him at the nest. As shown above she sometimes quit bowing before he did, but soon she got into the swing of things. They’ve been courting several times a day.

As she does before egg laying, Dorothy has begun hanging out at the nest. Here she stands at the nest in an “egg-y” position. Yesterday I saw her dig the scrape.

And she spent last night at the nest.

Will they raise a second family this year? No. There is no record of peregrines ever fledging two broods per year in North America. Our young peregrines must become independent no later than September. It takes four to five months to raise a peregrine from egg to self-sustaining juvenile. There just isn’t time.

And the sun will have its effect. After this Friday’s solstice the days will get shorter and Dorothy and E2’s breeding hormones will decline. Soon they’ll stop courting and begin their summer life, lounging and molting.

We all recognize the Doppler effect when an ambulance siren rises in pitch as it speeds toward us, then drops as it recedes. (Click here for a car horn example.)

Here’s a bird that uses that sound effect.

American avocets have many techniques for protecting their nests from predators. They pretend to incubate a fake nest, then walk a few steps and pretend again. They distract the predator by walking toward him in a teetering tightrope walk with wings outspread. And they mob aerial predators before they can reach the nests.

But the most amazing technique is reserved for ground predators. When avocets swoop to chase them away they shout at them, modulating their pitch to resemble the Doppler effect. This is done so convincingly that the predator thinks the bird is approaching much faster than it actually is. Run away!

Tex Sordahl discovered this while studying American avocets and black-necked stilts in the 1970s and ’80s. Both use the Doppler sound effect. I’m sure he got a dose of it during his study.

(photo by Ingrid Taylar via Wikimedia Commons. Click on the image to see the original.)

It’s been mulberry season for two weeks now. In our house it means we take off our shoes.

White mulberries (Morus alba) were imported from China in colonial times in hopes of starting a silk-making industry. If you import the silkworms and their host, of course you’ll get silk. Not! The silkworms died but the trees did not. They now hybridize with native red mulberry and are considered invasive.

On the plus side, white mulberries produce a lot of fruit for people and birds. We make the fruit into jams and jellies, the birds lead their fledglings to the trees where they safely sit and eat.

The problem is the fruit is prolific and falls readily from the trees. One tree in particular shades the sidewalk on our path through Magee Field to Schenley Park. Right now the sidewalk looks like this.

The fruit is unavoidable even if you walk in the grass. The berries squish underfoot (quite unpleasant!) and smash into the ridges on the bottoms of our shoes. The juice stains the carpet if you don’t clean it immediately.

So we’ve adopted the Japanese in-house shoe tradition. In mulberry season we take off our shoes.

These inch-long flowers are blooming now in Schenley Park. They stand out because the plant is three feet tall.

Though penstemons are common in the western U.S. Penstemon digitalis is one of the few species native to Pennsylvania. I found several blooming in a new location in the park, probably because their seeds were in a native plant mix applied to an erosion project.

Their scientific name is easy to remember. The common name is a mouthful: Foxglove beardtongue. Try saying that three times fast.

(photo by Kate St. John)

p.s. The pistil in this flower looks like a tongue and it has hairs, thus “beardtongue.”

Peter had just gotten off the bus to come watch Pitt’s peregrine family but instead of finding E2 and his son in the air, he found Silver Boy’s body in the middle of Forbes Avenue in front of the art museum. He’d been hit by a car. One of his parents was on Heinz Chapel steeple, staring at the spot where Silver Boy died.

We got permission from the Game Commission to bury this year’s only fledgling. Peter dug the hole and we said goodbye.

June is “air show” month for our local peregrines. Where the nests have emptied the action is in the air.

After they fledge, young peregrines are dependent on their parents for six to ten weeks while they learn to supply their own food.

Fortunately, as with all predators, they’re born with an instinct to hunt. Kittens instinctively stalk and pounce. Peregrines are programmed to chase. This means they can develop hunting skills without much parental assistance — which is why hacking works.

In their first weeks after fledging, juvenile peregrines chase anything that flies: their parents, their siblings, butterflies, even turkey vultures.

After two to three weeks they begin to focus on prey the right size. Eventually they capture something, almost by surprise.

In the meantime they play at all the right moves: chasing, mock dogfights, roll-overs, talon grappling and prey exchanges.

Above a juvenile in Wilmington, Delaware chases his sibling who won the prize.